sources which must switch fuels due to a lack of adequate fuel supplies, and

sources required to be modified as a result of Environmental Protection Agency regulations where no exemption
from such regulation is available to the source. An exemption under this Rule shall not be granted unless:

The applicant demonstrates that it made its best efforts to obtain sufficient emission offsets to comply with
Rule 421.C. and that such efforts were unsuccessful; and

The applicant has secured all available emission offsets and will continue to seek the necessary offsets and
apply them when they become available.